Groundwater Remediation at the North Indian Bend Wash Superfund Site

M&A has played a key role in developing, gaining regulatory approval for, and implementing all aspects of the groundwater remedy for this site. Our work has included source identification and delineation, remedy evaluation and selection, and preparation of the second 5-Year Review. Throughout this process, we have adapted to constraints associated with the end use — principally municipal supply — and the changing needs of water providers.

Overview

Located in the East Salt River and Paradise Valley groundwater basins, NIBW was added to the EPA’s Superfund list in the early 1980s after VOCs were detected at several municipal supply wells. Soil and groundwater characterization efforts uncovered a regional plume caused by multiple historical industrial facilities.

Services

Working initially on behalf of Motorola and later representing the entire group of participating companies, M&A has been integrally involved in the project since its inception, providing hydrogeologic investigation, remediation, and strategic management services.

Contaminant Investigation

  • Characterized the distribution, magnitude, and movement of VOCs in a deep, multi-layer, alluvial groundwater basin
  • Identified potential source areas based on historical facility data and VOC concentrations in vadose zone sediments and the uppermost aquifer

Groundwater Remediation

  • Developed capture / containment approaches for various components of the groundwater remedy
  • Developed a vadose zone remediation program using soil-vapor extraction (SVE) technology
  • Used the results of monitoring and modeling to assess the performance of the SVE system, develop criteria for program termination, and support the close-out of several source-control programs
  • Evaluated various components of the pump-and-treat remedy to evaluate and optimize capture and mass removal
  • Designed and oversaw the construction and testing of monitoring and extraction wells

Litigation Support

  • Analyzed hydrogeologic and water quality data to develop technical arguments regarding responsibility for groundwater contamination
  • Projected long-term capital and O&M costs for remediation to support settlement negotiations between PRPs based on assumptions about the probability of potential outcomes
  • Represented Motorola in an alternate dispute resolution process to allocate costs for operating a pump-and-treat-system
  • Provided technical support to develop and later renegotiate cost-sharing approaches for pump-and-treat activities between potentially responsible parties

Groundwater Modeling

  • Modeled the vadose zone at various source areas to assess the potential threat to groundwater from VOCs and the need for continuing SVE
  • Supported initial development of a site-wide, groundwater flow and solute-transport model and assumed responsibility for periodically updating and recalibrating it
  • Used the model to evaluate contaminant movement, assess plume containment under a range of extraction regimes, and compare the effectiveness of remedial alternatives
  • Applied a particle-tracking approach to assess remedy performance and demonstrate long-term protectiveness as part of two 5-Year Reviews

Permitting & Compliance

  • Designed and implemented long-term monitoring programs and evaluated data to verify plume containment and compliance with established performance metrics
  • Prepared materials for regulators, stakeholders, and a community involvement group
  • Interfaced with state and federal regulatory agencies to provide status updates and negotiate technical aspects of the remedy
  • Developed a site-wide relational database for water level / quality data, featuring a dashboard with menu-driven queries to output data, maps, tables, graphs, and reports